In conventional communications networks, voice and data communications services are commonly provided to customer premises via so-called “local loop” connections between a main distribution frame located at a Central Office and a respective demarcation point at each customer premise. A local loop is normally constructed as a pair of copper wires (commonly referred to as “tip” and “ring”, respectively), which may be either twisted together or flat untwisted. Copper wire local loops are commonly used to carry both voice communications (i.e. “Plain Old Telephone Service”, POTS) and data signals using Digital Subscriber Line (DSL) and its successors, for example.
In order to provide data services through the local loop, it is common practice to install a distribution frame or Serving Area Interface (SAI) of the type illustrated in FIG. 1. The SAI may be installed at a Central Office or in a cabinet between the Central Office and a plurality of customer premises. As may be seen in FIG. 1, the SAI 100 generally comprises a PSTN interface panel 102; a Line interface panel 104; a Digital Subscriber Line Access Multiplexer (DSLAM) 106; a splitter 108 connected to the DSLAM 106 via a plurality of DSL ports 110 and each of the PSTN and Line interface panels 102, 104, and a power supply module 112.
The PSTN interface panel 102 is configured to support POTS signalling to and from the main distribution frame (not shown) and to protect the splitter 108 and DSLAM 106 from over-voltage surges due to lightning, for example. The PSTN interface panel 102 comprises a plurality of sockets 114, each of which is connected to a respective PSTN wire pair 116 extending between the SAI 100 and the main distribution frame. A respective pair of jumper wires 118 is provided for connecting each socket 114 to the splitter 108. Similarly, the Line interface panel 104 is configured to support signalling to and from equipment at a customers' premises. The Line interface panel 104 also comprises a plurality of sockets 120, each of which is connected to a respective wire pair 122 extending between the SAI 100 and a demarcation point (not shown) at a customer premise. A respective pair of jumper wires 124 is provided for connecting each socket 120 of the Line interface panel 104 to the splitter 108.
With the arrangement of FIG. 1, the splitter 108 provides a signal path for POTS signalling between a respective pair of sockets 114, 120 on the PSTN and Line interface panels 102, 104 (and so between the main distribution frame and customer premised equipment), and also provides a connection for data service signalling between the DSL ports 110 and appropriate sockets 120 on the Line interface panel 104 (and so between the DSLAM 106 and a customer premised modem).
FIG. 2A illustrates a socket 114 of the type commonly used in the PSTN interface panel 102. As may be seen in FIG. 2A, the socket 114 comprises a pair of ports 200, 202 (labeled as “A” and “B”) associated with each of the tip and ring wires, and a ground port 204 which may be connected to a ground bus bar (not shown). For example, the “A” ports may respectively be connected (usually by conventional wire wrapping techniques) to tip and ring wires 116 extending outside the SAI 100 (i.e. to the main distribution frame), and the “B” ports may respectively be connected to tip and ring jumper wires 118 (usually by conventional wire wrapping techniques) extending between the socket 114 and the splitter 108. Typically, the sockets 120 of the Line interface panel 104 will be identical to the sockets 114 of the PSTN interface panel 102. Similarly, the “A” ports of sockets 120 may be connected (e.g. by conventional wire wrapping techniques) to tip and ring wires 122 extending outside the SAI 100 (i.e. to the demarcation point at the customer premise), and the “B” ports may be connected to tip and ring jumper wires 124 (e.g. by conventional wire wrapping techniques) extending between the socket 1120 and the splitter 108.
Referring to FIG. 2B, there is shown a primary protection plug 206 which is configured to complete the connection path between the tip and ring “A” and “B” ports while at the same time providing protection against over-voltage surges due to lightning strikes, for example. Thus, in the example of FIG. 2B, the plug 206 includes a first pair of pins 208 connected to a respective metal contact 210 that connects the tip wire “A” and “B” ports 200 to each other and to a surge arrestor 212 such as a Gas Discharge Tube (GDT). A second pair of pins 214 are connected to a respective metal contact 216 that connects the ring wire “A” and “B” ports 202 to each other and to the surge arrestor 212. A third metal contact 218 extends between the surge arrestor 212 and a ground pin 220 configured to insert into the ground port 204 of the socket 114, and so provides an electrical path to ground for surge currents. FIG. 2C schematically illustrates the electrical connections within the plug 206. It will be seen that inserting the plug 206 into the socket 114 completes the connection between the “A” and “B” ports and so between the tip and ring wires of a respective wire pairs 116 118 extending outside the SAI 100 (i.e. to the main distribution frame) and to the splitter 108, while at the same time protecting the splitter 108 and DSLAM 106 from over-voltage surges due to lightning strikes, for example.
In the North American market, the socket and protection plug are required to provide surge protection. The characteristics of the power surges (such as peak current, peak voltage and duration) are specified in published specifications, including:                Underwriters Laboratories UL 497, Standard for Safety for Protectors for Paired-Conductor Communications Circuits;        Telcordia GR-974-CORE, Generic Requirements for Telecommunications Line Protector Units (TLPUs);        Telcordia GR-2916-CORE, Generic Requirements for a 5 Pin Protector Block Assembly; and        Telcordia GR-1089-CORE, EMC and Electrical Safety—Generic Criteria for Network Telecommunications Equipment.        
Successor specifications are expected to be published in the future and will contain the same or updated power surge characteristics. Importantly, the power surge characteristics defined in these specifications exceed the limits of connectors and devices commonly used in electronic devices. This is the primary reason for the use of wire-wrap connections and Gas Discharge Tube surge arrestor devices 212 in the sockets 114 and primary protection plugs 206 described above.
Low-cost techniques for simplifying wiring within the SAI 100 and for supporting an increased number of connections in an SAI 100 of a given size would be desirable. More broadly, low-cost techniques for interconnecting wire-pair communications lines while providing surge protection in accordance with North American standards, would be desirable.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.